Toward Green Bridge Standards
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SUPPLEMENT TO PERSPECTIVE Sustainable Bridges Traditionally, bridge designs are transportation, etc., not only for today’s Raymond Paul Giroux, M.ASCE culmination of a selection process needs, but also for the needs of future that considers all of these criteria generations. The I‐35W Minnesota Bridge collapse in and balances the trade‐offs and August of 2007 was a stark reminder compromises between competing In June 2008, the Brookings Institute of the sometimes fragile state of criteria. For example, society may want Metropolitan Policy Program published our bridges. Bridge failures have many of their bridges to be works of art; a report titled “A Bridge to Somewhere: a devastating impact, not only in the however, the financial burden would Rethinking American Transportation potential for loss of human life, but also likely be too great for society to sustain. for the 21st Century”. The report the impact their failures have on our Likewise, a multi‐span, or short‐span highlights our country’s future local, regional, and national economies. bridge may be the least costly to build transportation challenges and offers To be sure, bridge failures are more than at a given site, but it may do irreparable some recommendations to improve just the highly visible catastrophic failures harm to the local environment. our infrastructure. Brookings Fellow; like I‐35W. Bridge failures also occur Renovation of existing bridges in‐place Robert Puentes, writes “We must when we have to reduce a bridge’s load is often the least expensive, but may recognize that we are on the cusp of capacity, or prematurely replace a bridge. also have a huge impact on road users a new wave of transportation policy. during construction. To be sure, there The infrastructure challenge of President There are about 600,000 bridges in is never any shortage of debate when Eisenhower’s 1950s was to build out our the United States. All of these bridges it comes to planning our major bridges. nation and connect within. For Senator play an important role in our country’s Moynihan and his colleagues in the transportation infrastructure. Our History shows there has never been 1980s and 1990s it was to modernize bridges span rivers, bays, canyons, a shortage of debate when we select the program and better connect roads, roads, and railroads; providing critical our major bridges. Historic bridges like transit, rail, air, and other modes. Today, connections and catalyst for commerce. the Brooklyn Bridge, the Golden Gate the challenge is to take transportation Inexpensive transportation is essential Bridge, and many other bridges were out of its box in order to ensure the to building and sustaining a prosperous debated for years before construction health, vitality, and sustainability of our economy and our bridges are one of the began. For example, it is said the metropolitan areas.” primary factors in determining what our Golden Gate Bridge took thirty million transportation costs will be. dollars and thirty million words to build. The report goes on to say, “America’s More recently, modern bridges like transportation infrastructure has failed Bridges, as structures, take a beating. California’s new San Francisco‐Oakland to keep pace with the growth and They are subject to large cyclical Bay Bridge, East Span, Buffalo’s new evolution of its economy. At the precise loadings, fatigue, extreme temperature Peace Bridge, St. Louis’ new Mississippi time when the nation desperately needs fluctuations, rain, snow and ice, deicing River bridge have all proven to be to prioritize its limited investments and chemicals, scour, accidental impacts, controversial. resources, the federal transportation and so on. And because of local site program has lost its focus.” conditions, each and every bridge design In 1983, David Billington, a professor of is unique. Accordingly, we demand more civil engineering at Princeton University In January 2009, the American of our bridges as compared to other authored the book, The Tower and the Association of Civil Engineers (ASCE) structures such as Bridge. He writes; “But it is in principle released its national “Infrastructure buildings and these demands dictate impossible to determine the least Report Card” and gave our nation’s an emphasis on the functionality of a expensive design because cost is a social overall infrastructure a grade of “D.” bridge’s design. measure and not a scientific one. Cost Further the report card concluded we depends not upon some laws of nature would need to spend a daunting $2.2 Obvious functional factors that affect but rather upon patterns in society; it trillion over the next five years to make bridge design include criteria such as: depends upon time and meaningful improvements. Bridges were site conditions, load capacity, span place.” given a grade of “C.” The report stated lengths, span widths, vertical clearance, that more than 26% of the nation’s seismic criteria, scour criteria, service As Billington suggests, patterns in bridges are either structurally deficient life, maintainability, constructability, and society do evolve. Most recently or functionally obsolete. The report life‐cycle cost. There are of course other we read and hear quite a lot about went on to say that a $17 billion annual factors such as context sensitive factors “sustainable solutions” as society investment in bridges would be needed including bridge aesthetics. comes to grips with the ever‐increasing to substantially improve current bridge demand on infrastructure in the face conditions. Currently only $10.5 billion Further, creating successful designs for of dwindling resources. Basically, to is spent annually on the construction major bridges is an evolving process. achieve sustainable bridges, ecological, and maintenance of bridges. With scientific and technical advances, economic, and social factors will all have engineers will explore the use of new to be considered in the development of The ASCE’s “Infrastructure Report materials and new methods of structural our future bridge programs. Sustainable Card” proposed five measures it analysis. At the same time when society development is the challenge we believes will help the country improve its demands iconic bridges, architects will face to be good stewards of society’s infrastructure: explore new shapes and forms. limited natural resources, energy, Web | ASPIRE, Spring 2010 SUPPLEMENT TO PERSPECTIVE • Increased federal leadership in “Engineers shall hold paramount the match his designs to each location’s infrastructure; safety, health and welfare of the public unique environment. He believed • Promote sustainability and resilience; and shall strive to comply with the that bridges should be a measured • Develop federal and regional principles of sustainable development balance of both form and function. infrastructure plans; in the performance of their professional All the while, McCullough was ever • Address life‐cycle costs and duties.” mindful of not wasting the taxpayer’s maintenance needs; and money. Accordingly, he paid a great • Increase and improve infrastructure While achieving sustainability may deal of attention to site conditions, investment from all stakeholders. seem like an overwhelming task, really stream behavior, durability, navigation it comes down to all of us doing our requirements, traffic considerations, This is a good list of recommendations, part. We all need to be aware of the architectural features, and available covering the “big‐picture” or global big picture, but there is much we funding. While McCullough never considerations all the way down to the can all do in our own arena. First and used the term “sustainability”, he details or local considerations to evaluate foremost, I would think “life‐cycle” most certainly practiced it. issues to improve the sustainability of cost or economy should be of primary our bridges. First, looking at the big importance in bridge design. This Today we face the challenge of picture, the ASCE recommendations concept is nothing new. maximizing transportation funding call for increased federal leadership in in today’s tough economic times. We promoting sustainability. In 1883, the Brooklyn Bridge was have an ever aging bridge inventory, completed. In 1944, some six decades and we have growing demand for more To gain better understanding of after its opening, pre‐eminent bridge and more bridges. Accordingly, proper the federal government’s role in engineer David B. Steinman wrote: management of our bridges is essential sustainable bridges, I talked to Mr. “The [Brooklyn Bridge] structure did to achieving sustainable bridge solutions Myint Lwin, director of Federal Highway not represent the contemporary style on a national, regional, and local level. Administration (FHWA) Office of Bridge in architecture. It had not a single Technology. Mr. Lwin has been a leader battlement, a single inset of red brick To stretch our transportation funds, the in promoting sustainability of bridges or white marble, a single scroll of ASCE has recommended development and the concept of “Green Bridges”. cheap ironwork, or a single panel of of federal and regional infrastructure He says, “In ‘Green Bridges,’ the design, gilded decoration. But later generations plans. FHWA’s Myint Lwin has written construction, and maintenance practices clearly see what the Roeblings’ about the importance of implementing should give full consideration to at least wrought. In an age of superficial integrated bridge management systems. the following areas: embellishment and pretentious He writes; “As transportation agencies atrocities the two bridge builders gave are facing limited resources,… for • Attention to safety, durability, mobility no thought to the prevailing fashion maintaining and preserving an efficient (traffic flow), and efficiency; in design. They were not architects, network of highways, it becomes ever • Compliance with environmental and but workmen seeking only to do an more important to invest the resources preservation laws and regulations; honest and sturdy job. How the thing in areas where benefit‐to‐cost ratios are • Application of context sensitive was going to work and how to make the highest.” solutions; it last were their chief concern.